It all started because of competitors shooting IPSC/USPSA Limited Class.

Cartridges that made MAJOR had a point scoring advantage over those that did not. The 45ACP had no trouble making MAJOR but it took a back seat to the 9MM Parabellum in the capacity department. Capacity was also a distinct advantage in IPSC/USPSA.

There were some folks that chose to exceed SAAMI specifications for the 9MM Parabellum cartridge and push the small cased round up to a MAJOR power factor. Some (not all) of these early pioneers of 9MM MAJOR made sure their firearms were built for the extra pressure and stress that this created. Heck, 9MM Parabellum brass was inexpensive and plentiful. So if you lost some or it only reloaded a few times it was no big deal.

Unfortunately many shooters that came after these initial pioneers pushed the 9MM Parabellum to these same levels in mostly stock firearms. This included many firearms that did not have ramped barrels or fully supported chambers. One result of this extra power was firearms that did not live long due to simple wear and tear. It was not only the accelerated wear, there were some spectacular spontaneous disassemblies that took place.

This eventually lead to a rules change that all firearms chambered for the Major 9MM cartridge would be classified as MINOR no matter what power factor they reached. The hope was that folks would stop pushing firearms beyond their safety limits. Cartridges like the 9x23 Winchester offered major power, but they need to be in the larger pistols to accommodate to longer cartridge overall length. To many that was a disadvantage.

Smith and Wesson saw an opportunity to design a cartridge with the same overall length and diameter as the more than century old 9MM Parabellum but with a different length case so it could not be accidentally used in a standard 9MM Parabellum barrel. This new cartridge was to be 9x21.5MM as opposed to the 9MM Parabellum's 9x19.15MM. In addition, the cartridge casing itself would be far stronger than the 9MM Parabellum's afterall this new cartridge was designed ip operate at 50,000PSI as opposed to the 9MM Parabellum's 35,000 PSI

Smith and Wesson partnered with Federal Cartridge to produce this brass, ammunition and to submit the cartridge to SAAMI. The only other ammunition manufacturer of notoriety to load this ammunition was Corbon. A few small commercial loaders offered the ammunition from time to time.

Thus the 356TSW was born, a cartridge that would once again fit into 9MM Parabellum sized firearms and be able to safely deliver MAJOR power factors.

At the time of it inception in 1992, TSW stood for Team Smith and Wesson. Later in life TSW was changed to Tactical Smith and Wesson

The 356TSW was well on it's way to being eligible in IPSC/USPSA Limited Class. The rules required that there be a minimum of 3 manufacturers producing the ammunition. Right at that point, the governing body made a rule change that MAJOR power factor required .400 diameter cartridges or above. I have no idea of the rules change was to prevent 356TSW from entering IPSC/USPSA Limited Class competition or for some other reason.

With the loss of the competition community, the 356TSW faded into obscurity in under a decade. The companies that loaded ammunition for it discontinued the practice and one of the big surplus houses blew out ammo at a price that I wish I had stocked up on.

Now that the power factor has been reduced, I believe all of the above contortions have evaporated and 9MM based cartridges are now once again eligible for MAJOR. Of Course with the lower power factor it is easy to make MAJOR safely in the 9MM Parabellum cartridge so the sport has no need for the 356TSW.

If Smith and Wesson had not been actively pursuing the 40 Smith and Wesson into the Law Enforcement community at the time the 356TSW was availble, the 356TSW could have found a home there. However, the FBI studies of the day supported the 40 Smith and Wesson.

Yes I know the two organizations rules differ and rules sometimes differ between countries, this is a composite of what I have been able to read over the years. If I have misquoted something, help me improve this document, if I missed something, let me know so it can be added in.